Henry Louis Gates practices genealogy for PBS's "Faces of America"

Eva Longoria and Yo-Yo Ma have a common ancestor.

It takes a long time and considerable patience to get to that surprise denouement of “Faces of America,” a four-part PBS series, beginning on Wednesday, about family roots by the Harvard professor Henry Louis Gates Jr. And even with charming celebrities — Meryl Streep, Mike Nichols and Queen Noor of Jordan are among the 12 whose genealogy is explored almost back to Paleolithic times — the telling can at times be a little wearisome....

Mr. Gates, the film’s narrator and writer, put a huge effort into this project, which is obviously dear to his heart. The director of the W. E. B. Du Bois Institute for African and African American Research at Harvard, Mr. Gates is a founder of the genealogy Web site AfricanDNA.com, and the editor in chief of The Root (theroot.com), a site on African-American news, culture and genealogy. He has also done two previous series about African-American genealogy for PBS....

At the time of [his] arrest, Mr. Gates was outraged, convinced that he was suspected of burglary only because he was black. Turns out, he isn’t even so black; in the film he reveals that like many African-Americans, he has white ancestors, and more European roots than African....

What is more surprising is how little some people know about their own histories. Queen Noor, who was born Lisa Najeeb Halaby into a family of Syrian Christian immigrants, says she was the only one in her successful, assimilated family to take a real interest in its Arab roots. But she didn’t know that her grandfather Najeeb, a first-generation immigrant, was buried in Brooklyn. Mr. Gates takes her to visit the gravestone for the first time. Queen Noor, who converted to Islam when she married King Hussein of Jordan in 1978, prays at the site....

“Faces of America” has moments of pomposity. But America is, after all, a nation of immigrants, and these kinds of stories have a fascination all their own.